@thor thats why it's no real week!!1
"Weeks start with Monday. Each week's year is the Gregorian year in which the Thursday falls. The first week of the year, hence, always contains 4 January. ISO week year numbering therefore slightly deviates from the Gregorian for some days close to 1 January. " https://en.m.wikipedia.org/wiki/ISO_week_date 😜
Fun aside, using weeks has to stop. Businesses do use it often here and it always drives me mad.